1. Field
The present invention relates to a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same, and more particularly, to a non-aqueous electrolyte with excellent high-temperature storage performance and excellent cycling performance, and a lithium secondary battery comprising the same.
2. Description of Related Art
With the recent development of information communication industries, the trends of electronic devices are moving towards mobility, reduced size, weight and thickness. Accordingly, the demand for high energy density of batteries as power sources of electronic devices is increasing. Lithium secondary batteries are gaining attention as the most favorable battery capable of satisfying this demand, and currently studies are being actively made on lithium secondary batteries. Lithium secondary batteries are made up of a cathode, an anode, an electrolyte, and a separator. The electrolyte and the separator provide a passage for lithium ions moving between the cathode and the anode. Lithium ion secondary batteries generate electric energy by the redox reaction during intercalation/disintercalation of lithium ions at the cathode and the anode.
A non-aqueous electrolyte used in a lithium secondary battery generally includes an electrolyte solvent and an electrolyte salt. During charge/discharge, the electrolyte solvent decomposes on the surface of an electrode or is co-intercalated between layers in a carbon-based anode, so that the structure of the anode may collapse. This may damage the stability of the battery.
It is known that these problems can be solved by a solid electrolyte interface (SEI) film formed on the surface of an anode through a reduction reaction of the electrolyte solvent when a battery is initially charged. However, the SEI film is insufficient to continuously protect the anode, and as the battery repeats charging/discharging, its life and performance deteriorate. Moreover, since the SEI film is thermally unstable, the SEI film may easily collapse due to electrochemical and thermal energy increasing over time, particularly when a battery is operated or left under high temperature conditions. For this reason, when the battery is placed under high temperature conditions, its performance further deteriorates. Once the SEI film collapses or the electrolyte decomposes, gas such as CO2 is continuously generated, which causes an increase in internal pressure and thickness of the battery.
As a solution to solve the above problems, suggestion has been made to add, to an electrolyte, vinylene carbonate (VC), succinic anhydride, or acrylic ester of pentaerythritol-based compound as an additive capable of forming a SEI film on the surface of an anode. Such succinic anhydride or acrylic ester of pentaerythritol-based compound has excellent high-temperature storage characteristics but exhibits poor cycling characteristics due to its high SEI resistance.